1. Field of the Invention
This invention relates to an endoscopic puncture needle to be introduced into a body cavity through a channel of an endoscope for aspiration biopsy, injection or the like.
2. Description of the Related Art
An endoscopic puncture needle of this type is used to make puncture by utilizing a channel of an endoscope, for example, for a biopsy of a tissue in a body cavity. The puncture needle comprises an outer sheath capable of being inserted through the channel of the endoscope, an inner sheath advanceably and retreatably inserted through the outer sheath, and a rigid needle element secured to the distal end of the inner sheath.
When an ultrasonic endoscope is used to stick the needle into a deep-positioned organ, such as the spleen, through a wall of an alimentary canal, such as the stomach and the duodenum, to examine a tissue, the needle element must have a puncture length sufficient to reach the tissue to be examined. Further, since the exit of the channel of the ultrasonic endoscope is positioned at one side of the field of view of the ultrasonic endoscope, the needle element must protrude obliquely toward the organ being observed via an ultrasonic tomography image, so that the protruding amount of the needle element should be large, thus the needle element is required to be as long as possible.
On the other hand, the length of the relatively rigid needle element is limited since the needle element must be advanced and retreated smoothly without being damaged through the relatively small channel of the endoscope when the endoscope is bent.
Under the circumstances, in conventional structures, the needle element tends to have a puncture length insufficient to reach the tissue to be examined. Even if the needle element has a sufficient puncture length, since the needle element connected to the distal end of the inner sheath is long, both of the outer and inner sheaths tend to be incapable of advancing and retreating through the channel when the endoscope is bent and when an treating instrument upheaving member is stood up. Thus, it is possible that a sure puncture operation is not performed.
Further, when an ultrasonic endoscope is used to puncture a deep-positioned organ, such as the spleen, through a wall of an alimentary canal, such as the stomach and the duodenum, to examine a tissue, a force capable of secure puncture of the deep-positioned organ through the alimentary canal must be transmitted to the distal end of the puncture needle. Moreover, the needle element must be advanced and retreated smoothly without being damaged through the channel of the endoscope when the endoscope is bent.
However, in conventional structures, the inner sheath is made of a flexible tube. Therefore, when the inner tube is pushed in to stick the needle element into a deep-positioned tissue, it is possible that the inner sheath made of the flexible tube is flexed within the outer sheath and that the force is not completely transmitted to the distal end of the puncture needle, thus sure puncture may not be accomplished.